The present invention relates to bailer lines for top head drive rotary well drills.
Three current types of well drilling apparatus are currently in predominant use for ground water drilling. They are the cable drive, the rotary table drill, and the top head drive rotary drills. All three forms are usually mounted to a truck frame and include a pivoted derrick. The derrick will move between a horizontal transport position and an upright operating position.
The cable drive drilling rig includes a drilling tool that is suspended by an elongated cable. The upper end of the cable is usually connected to a winch and a walking beam arrangement that will alternately raise and drop the drilling tool. The well bore is formed by impaction of the drill tool against the ground surface. Operation of cable drive drilling rigs requires a great amount of skill in timing of the impaction strokes, especially as the drilling tool bores deeper into the earth.
The cable tool drilling rigs inherently include "bailers" as well as other auxiliary winch-hoist arrangements that are generally driven mechanically. However, cable tool drilling rigs are presently outdated by the faster and easier-to-operate rotary drills. Additionally, cable tool rigs are primarily mechanically driven and modern auxiliary hydraulic equipment may not be added without extensive modification and further complication of the working mechanics.
A more modern development in well drilling equipment is the rotary drive drill utilizing a "table drive". The rotary drive drills include rotary drill bits at downward ends of elongated rigid steel drill strings. The drill strings are rotated at the drilling rig and progressively lowered as the rotating bit operates. Sections of the drill string are added at regular intervals while the well is being bored and are removed in sections as the drill string is raised.
The table drive rotary drill includes an upright derrick and a drive unit at the derrick base. The drive unit is termed the "table" and is powered to rotate an elongated upright "kelly". The kelly is generally of polygonal cross section and vertically movable within the table drive. The lower end of the kelly is connected to the upper end of the drill string and is simultaneously rotated and forced downwardly to feed the drill string down the hole and produce pressure on the boring head. After the top end of the kelly reaches the table, the entire drill string must be hoisted with the kelly to bring the top of the drill string to the table level. The drill string is then gripped so the kelly can be removed. A new drill string section is then attached to the string which is again lowered. The kelly is then connected to the top end of the new section. These steps are repeated until the well bore is completed.
Well casing, a continuous pipe placed in the drilled hole to hold the sidewalls from caving in and to keep the well sanitary, is placed in a separate operation after the well hole has been completed. This involves removing the drill string and tool from the hole and successively lowering jointed casing sections down the hole to the bottom.
A solution to the slow operation of the cable drive drill rigs and in many instances the table drive rigs, is the "top head drive" drill rig. The distinguishing characteristic of the top head drive from the table drive is provision of a vertically movable "top head" drive mechanism that moves vertically along the derrick to attach and move with the top end of the drill string. No kelly is required and the position of the top head over the bore opening allows for simultaneous insertion of drill casing as the hole is being bored. Therefore, a top head drive rotary drill can operate significantly faster than table drive or cable drive drilling rigs.
One difficulty with top head drive drilling rigs occurs in areas where sandy soil is prevalent. Loose sand or mud can partially fill a drilled hole even though the hole has been simultaneously lined with casing. The hole must therefore be cleaned and a sand screen placed before a pump can be set.
An effective and proven method of cleaning sand or other debris from a drilled hole is through use of the "sand line". An elongated, hollow bucket is lowered by cable down the hole. The bucket has a hinged flap on the bottom that will open up into the bucket but will not open downwardly. Impact of the bucket with the sand causes the flap to open and sand will fill the interior. The bucket is then lifted. The flap will close under the weight of the sand above and can be raised to the surface and dumped. The bucket is generally connected to a bailer on the derrick or frame of the drill rig for accomplishing this function.
Bailers have not been standard items supplied with top head drive drilling rigs. The mechanism of the drive head and components for raising it up and down the derrick inhibit the use of a bailer line. Furthermore, it is reasoned that where a hole can be lined simultaneously with the drilling process, there is no need or use for a bailer. However, the loose sand situation as described above is only one in which a bailer provided on a top head drive derrick would be useful indeed. Known forms of bailers for cable drive and table drive rigs are extremely slow, underpowered, and both bulky and complex in nature. Table drive bailers are typically driven by a nonpositive displacement hydraulic motor coupled to a mechanical gear reduction unit. Two hydraulic lines must therefore be attached between the hydraulic fluid source and motor. A hydraulic brake must also be supplied for controlling the down hole speed when the bailer is used to lower the equipment down the hole. Such a brake can be effective in controlling lowering speed which is a considerable problem with heavy equipment. Without some form of speed reduction mechanism, increasing down hole speeds can overcome the braking effect of a nonpositive displacement motor. This results in free fall and damage to the down hole equipment in addition to the bailer components. The problem the hydraulic brake presents, though, is its complexity and the additional requirement of more hydraulic fluid lines and associated control valves to already over-complex hydraulic systems.
Many current top head drive rigs make use of "jib" "hoists" to raise and lower casing and drill sections and, on occasion, to raise and lower equipment down the hole. The typical jib hoist is painfully slow and does not include enough cable to reach the bottom of deep wells. Other resources are usually sought with deep hole situations and when more than one round trip needs to be made up and down the hole (as with the sand bailing example set forth above). When bailing or similar operations are required, either the top head rig is moved and replaced with a cable drive rig (that has a bailer) or a "pump truck" with a pump setting hoist is positioned next to the hole adjacent the derrick. Both alternatives are very inconvenient. The least inconvenient of the two (using the pump truck) at best take the pump truck and its operator away from their intended duties, notwithstanding the mechanical and safety hazards of positioning the pump hoist boom correctly over the well without first moving the drill rig or lowering the derrick. The additional equipment crowded about the bore hole makes operations inefficient to say the least. In addition, the boom of a pump truck is generally substantially shorter than the drill derrick so special arrangements must be made when the pump truck is used to handle drill stem sections, casings, and other apparatus designed particularly for the taller drilling rig derrick.
It therefore becomes increasingly desirable to provide a bailer attachment for existing top head drive drill rigs that will mount to the derrick in an unobtrusive position and that will function to both lift and lower heavy loads along a drill hole with minimal control requirements and with minimal interference with respect to existing hydraulic power supply systems.
It is also desirable to provide a bailer attachment for top head drive drill rigs that includes a direct drive relationship between the bailer drive motor and winch drum to thereby reduce mechanical complication and also reduce the number of hydraulic components, lines, and controls utilized for such an attachment.